Cecil, was it you that mention a "windom balun?"
 

On 9/14/2010 5:09 PM, Owen Duffy wrote:

...
It would not surprise me if the common mode choke consumes a significant
portion of transmitter power on some bands, the portion will depend a lot
on your own scenario.

Owen

Yep, why I don't like windoms ... unless he has discovered a zero point
energy source, his RF IS heating those beads ...

Regards,
JS

Cecil, was it you that mention a "windom balun?"
 

On Sep 14, 5:51*pm, John Smith wrote:
OK, I'll ask, "I am correct in thinking that most are using a 'voltage
balun' (ruthroff 1:4) as the 'Low Loss Matching Transformer' and a
'current balun' (guanella 1:1) as the 'Special-High Isolation Line
Isolator?'"

That's the theory behind the Carolina Windom. Whether it actually
performs up to expectations is questionable. The marketing hype
acknowledges that the 4:1 voltage balun will cause common-mode current
on the coax which is expected for off-center-fed dipoles. They seem to
assume that the "Isolator" located 20 feet from the dipole feedpoint
is an ideal device with an infinite choking impedance. If it were
that, the antenna would work exactly as advertised. Unfortunately,
there's no such thing as an ideal isolator so we are zeroing in on
what is possible in reality and what must remain as marketing hype.
From my modeling, it appears that the isolator works well for any
frequency where the length of the coax from the feedpoint to the
isolator is approximately an odd multiple of 1/4WL. That occurs on 20m
and 10m. Unfortunately, my modeling indicates that RF-in-the-shack may
be a problem on 40m and I would be tempted to add an ugly balun.
--
73, Cecil, w5dxp.com

Cecil, was it you that mention a "windom balun?"
 

On 14 sep, 17:34, Owen Duffy wrote:
lu6etj wrote :

...





For monoband applications we can get more Z from a coaxial choke
making the winding for autorresonance. K1TTT have a good data table.

Time ago I want test differents antenna to lift with a kite and I
found =
http://www.io.com/~n5fc/rfd.htm, the idea seems to me interesting
enough to make some test that are descibed here =

http://www.solred.com.ar/lu6etj/tecn...ga_revisada-en
.htm

from here I think of another use of de "coaxial trap" to get more Z
from coaxial winding specially in monoband antennas, I named de
critter "The Trap balun" *=

http://www.solred.com.ar/lu6etj/tecn...a_balun-en.htm

4NEC2 simulations and real field test show me both approachs works
fine :)

How did you arrive at the value of Q (=100) used in the modelling. Was it
measured, or guessed?

Based on some experimental work, I expect that the effective RF
resistance of a closed space solenoidal coil of braided coax is much
higher than the same straight length a copper cylinder.

BTW, if you want to make a more compact self resonant trap on the lower
HF bands, wind the coil in two layers. The article athttp://vk1od.net/antenna/7MDipole/7MDipole.htmshows a pic of a two layer
7MHz self resonant balun made with IIRC about 6 turns per layer of RG6.

Owen- Ocultar texto de la cita -

- Mostrar texto de la cita -

I do not remember Owen, I believe Q 100 was a number for the text
example, calculated Q on 7 MHz for ideal coil was about 400 and
measured real coaxial made coil with a GR-1606 A near 200. at that
time I did not think to use RG6, It is more light than RG58, isn't it?
Seven turns of RG 58 on 63 mm diameter with parallel condenser it was
very light, enough for the purpose, Rokkaku lifted 40 m "syringe"
antenna flied very well.

R, to two layers choke. Well... frankly to me common mode radiation it
is not something I lose sleep, I have not troubles in my shack and I
was not very lucky in all attempts to reduce nasty modern suburban
noise with baluns + chokes + grounded points, so many noisy companies
and neighbors cables around :( antenna height showed much better
results.

73

Miguel LU6ETJ

Cecil, was it you that mention a "windom balun?"
 

On Tue, 14 Sep 2010 21:18:00 -0400, "Ralph Mowery"
wrote:

It got warm, but not hot
after about 5 minuits of applied power while hooked to the antenna.

Hi Ralph,

Then the loss is trivial. On 80M the Z should be sufficiently high
enough to prevent a large current to develop a node at that point on
the line - it remains to be seen if you need another one further down
to suppress induced current that would then slide into your shack (you
would be complaining of it by now, however).

73's
Richard Clark, KB7QHC

Cecil, was it you that mention a "windom balun?"
 

On 9/14/2010 5:09 PM, Owen Duffy wrote:
"Ralph wrote in
m:

...
That is what I am using on a home built version. Using a 4:1 voltage
balun at the feedpoint and the ferrite bead type about 20 feet down
from the feedpoint.

The ferrite choke is doing something as it gets warm while running
around about 1 KW to the antenna. Doesn't heat up when going into a
dummy load.

I am not surprised at your results with a dummy load. If it is a well
screened unbalanced dummy load, you should expect zero dissipation in the
balun cores.

The fact the balun cores are heating in the antenna scenario indicates
there is some common mode current. You probably have no idea of the
current.

Something to keep in mind is that the average power of uncomressed voice
SSB is about 3% of PEP, so if your 1kW was uncompressed voice SSB, the
average transmitter power might be more like 30W, or half that in a 50:50
over scenario over the long term.

Another thing is the ferrite toroids heat and cool very slowly, so the
operating temperature might still be rising half an hour after the
transmitter is applied (so long as you haven't exceeded their Curie
temperature).

It would not surprise me if the common mode choke consumes a significant
portion of transmitter power on some bands, the portion will depend a lot
on your own scenario.

Owen

Even worse than that! A lot will only consider the loss in the
transmitted signal of such an antenna, perhaps even call it "trivial."
However, the received signal will suffer from exactly the same losses
.... while even losing 500 watts of a 1KW signal can be considered
"trivial", losing 50% of ones received signal is NOT!

Regards,
JS

Cecil, was it you that mention a "windom balun?"
 

Even worse than that! A lot will only consider the loss in the
transmitted signal of such an antenna, perhaps even call it "trivial."
However, the received signal will suffer from exactly the same losses
... while even losing 500 watts of a 1KW signal can be considered
"trivial", losing 50% of ones received signal is NOT!

Regards,
JS


3dB is still only 3dB regardless of where it happens in the link budget!!

Jeff

Cecil, was it you that mention a "windom balun?"
 

On Sep 15, 6:18*am, John Smith wrote:
... while even losing 500 watts of a 1KW signal can be considered
"trivial", losing 50% of ones received signal is NOT!

That depends on the signal to noise ratio. If the signal to noise
ratio remains the same while 50% of one's signal is lost, the dynamic
range of a low-noise HF receiver usually makes up for it. Witness the
Beverage antenna where 99% receive power loss is tolerated: (from
Wikipedia)

"While Beverage antennas have excellent directivity, because they are
close to lossy earth they do not produce absolute gain (typically -20
to -10 dBi). This is rarely a problem, because the antenna is used at
frequencies where there are high levels of atmospheric radio noise."
--
73, Cecil, w5dxp.com

Cecil, was it you that mention a "windom balun?"
 

On 9/15/2010 4:51 AM, Cecil Moore wrote:

...
That depends on the signal to noise ratio. If the signal to noise
ratio remains the same while 50% of one's signal is lost, the dynamic
range of a low-noise HF receiver usually makes up for it. Witness the
Beverage antenna where 99% receive power loss is tolerated: (from
Wikipedia)

"While Beverage antennas have excellent directivity, because they are
close to lossy earth they do not produce absolute gain (typically -20
to -10 dBi). This is rarely a problem, because the antenna is used at
frequencies where there are high levels of atmospheric radio noise."
--
73, Cecil, w5dxp.com

Cecil,

If a mere loss of 10% drops you too close to the sensitivity threshold
of your receiver, your ability to pull out a weak signal just suffered
the kiss of death ... 100w on a kw might not even be noticed on the
other end ...

Regards,
JS

Cecil, was it you that mention a "windom balun?"
 

In message , John Smith
writes
On 9/15/2010 4:51 AM, Cecil Moore wrote:

...
That depends on the signal to noise ratio. If the signal to noise
ratio remains the same while 50% of one's signal is lost, the dynamic
range of a low-noise HF receiver usually makes up for it. Witness the
Beverage antenna where 99% receive power loss is tolerated: (from
Wikipedia)

"While Beverage antennas have excellent directivity, because they are
close to lossy earth they do not produce absolute gain (typically -20
to -10 dBi). This is rarely a problem, because the antenna is used at
frequencies where there are high levels of atmospheric radio noise."
--
73, Cecil, w5dxp.com

Cecil,

If a mere loss of 10% drops you too close to the sensitivity threshold
of your receiver, your ability to pull out a weak signal just suffered
the kiss of death ... 100w on a kw might not even be noticed on the
other end ...

As a Windom is only likely to be used on the HF bands (and probably
mainly on the lower HF bands), I would have thought that a few dB of
attenuation would have negligible effect on the SNR.
--
Ian

Cecil, was it you that mention a "windom balun?"
 

On 9/15/2010 5:30 AM, Ian Jackson wrote:

...
As a Windom is only likely to be used on the HF bands (and probably
mainly on the lower HF bands), I would have thought that a few dB of
attenuation would have negligible effect on the SNR.

There are "Windom only baluns?" I thought that was something they just
told the newbies!

Regards,
JS